diff --git a/dlls/msi/custom.c b/dlls/msi/custom.c
index 160754a91b3..b250b1b068e 100644
--- a/dlls/msi/custom.c
+++ b/dlls/msi/custom.c
@@ -589,7 +589,7 @@ UINT CDECL __wine_msi_call_dll_function(const GUID *guid)
 
 static DWORD custom_start_server(MSIPACKAGE *package, DWORD arch)
 {
-    static const WCHAR pipe_name[] = {'\\','\\','.','\\','p','i','p','e','\\','m','s','i','c','a','_','%','x',0};
+    static const WCHAR pipe_name[] = {'\\','\\','.','\\','p','i','p','e','\\','m','s','i','c','a','_','%','x','_','%','d',0};
     static const WCHAR msiexecW[] = {'\\','m','s','i','e','x','e','c','.','e','x','e',0};
     static const WCHAR argsW[] = {'%','s',' ','-','E','m','b','e','d','d','i','n','g',' ','%','d',0};
 
@@ -605,9 +605,11 @@ static DWORD custom_start_server(MSIPACKAGE *package, DWORD arch)
         (arch == SCS_64BIT_BINARY && package->custom_server_64_process))
         return ERROR_SUCCESS;
 
-    sprintfW(buffer, pipe_name, GetCurrentProcessId());
+    sprintfW(buffer, pipe_name, GetCurrentProcessId(), arch == SCS_32BIT_BINARY ? 32 : 64);
     pipe = CreateNamedPipeW(buffer, PIPE_ACCESS_DUPLEX, 0, 1, sizeof(DWORD64),
         sizeof(GUID), 0, NULL);
+    if (pipe == INVALID_HANDLE_VALUE)
+        ERR("Failed to create custom action client pipe: %u\n", GetLastError());
 
     if (sizeof(void *) == 8 && arch == SCS_32BIT_BINARY)
         GetSystemWow64DirectoryW(path, MAX_PATH - sizeof(msiexecW)/sizeof(WCHAR));
diff --git a/programs/msiexec/msiexec.c b/programs/msiexec/msiexec.c
index 47cef7e0fa2..ead3bfb9dea 100644
--- a/programs/msiexec/msiexec.c
+++ b/programs/msiexec/msiexec.c
@@ -406,7 +406,7 @@ static DWORD CALLBACK custom_action_thread(void *arg)
 
 static int custom_action_server(const WCHAR *arg)
 {
-    static const WCHAR pipe_name[] = {'\\','\\','.','\\','p','i','p','e','\\','m','s','i','c','a','_','%','x',0};
+    static const WCHAR pipe_name[] = {'\\','\\','.','\\','p','i','p','e','\\','m','s','i','c','a','_','%','x','_','%','d',0};
     DWORD client_pid = atoiW(arg);
     DWORD64 thread64;
     WCHAR buffer[24];
@@ -423,7 +423,7 @@ static int custom_action_server(const WCHAR *arg)
         return 1;
     }
 
-    sprintfW(buffer, pipe_name, client_pid);
+    sprintfW(buffer, pipe_name, client_pid, sizeof(void *) * 8);
     pipe = CreateFileW(buffer, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
     if (pipe == INVALID_HANDLE_VALUE)
     {